The present invention relates generally to the dental industry and, more particularly, to dental tools which are used in the production of dental cast models.
In the dental industry, technicians commonly use dental tools to construct a dental cast model of the mouth of a patient. The dental cast model comprises an upper jaw model and a lower jaw model which are typically affixed to one another by an articulator. An articulator is a device comprising upper and lower mounting platforms which are connected to the upper and lower jaw model elements. The articulator enables for centric, lateral and protrusive movement of the upper jaw model relative to the lower jaw model in order to closely simulate the relationships and the actual movement, or bite, of the mouth of the patient.
Various types of devices and procedures have been used in the art for creating a dental cast model.
One method for manufacturing dental cast models which is well known and commonly used in the art involves the execution of a molding process by a dental technician. Specifically, one or more plastic trays filled with impression material are used to create a negative impression of the full dental arch of a patient. The negative impression is then filled with a casting material, such as dental stone or epoxy. The impression tray is then inverted and mounted upon a pre-formed mounting device, such as a dental cast tray or base. After the casting material has had an opportunity to harden, the impression tray is removed so that the casting material forms a positive dental impression on the mounting surface.
Molded dental models are often used to manufacture crowns, bridges, inlays, dentures and other dental prosthetics outside of the mouth of the patient. The construction of dental prosthetics typically necessitates the ability to remove each individual model tooth, or die, from its spatial physical relationship to the remainder of the jaw model for the purpose of constructing accurate margins and contours. In the event that two or more individual units of bridgework are to be joined, it is necessary that the working model segments be accurately and repeatedly returned to their original relationships precisely as it or they existed prior to any cutting, separations or disassembly of the jaw model.
In order to effectively remove an individual model segment from the remainder of the dental model, the entire jaw model is typically removed from the mounting device and positioned upon a cutting surface. A cutting device, such as a saw, can then be used to separate the desired model teeth from the remainder of the dental model. After the technician has completed manufacture of the dental work, the dental model can be re-assembled onto the mounting device.
It should be noted that during the re-assembly of the dental cast model, it is essential that precise registration and desired occlusal alignment be maintained between the working model segments and the remainder of the molded jaw model.
In U.S. Pat. No. 5,506,095 to L. E. Callne, there is disclosed a dental tray cast subassembly for forming a dental cast model and for mounting to a dental articulator. The tray subassembly forms a channel shaped in a configuration of a human jaw to receive a mold material for forming a dental cast model. The channel further includes ribs for registering the model relative to the channel and a release mechanism for releasing the model from the channel. Further included is a platform for interconnecting with connectors for connecting the subassembly to an articulator.
Dental tray cast subassemblies of the type described above in Callne have been found to be undesirable because the casting material is used as an alignment device for returning the working model segments to the remainder of the molded jaw model. Specifically, the mold material adheres to and conforms with the material of the dental cast model and thereby serves as an alignment means for assuring proper registration of the dental cast model onto the dental articulator. However, because plasters are a relatively distortive material which can fragment over time, proper re-alignment of the working dental model back onto the remainder of the molded jaw model is not guaranteed, which is highly undesirable.
In U.S. Pat. No. 5,393,227 to W. H. Nooning there is disclosed a dental impression handling tool and method. The dental impression handling tool consists of two base structures shaped to approximate two opposite quadrants of a full dental arch, and two similarly-shaped inserts that snap fit into the base structures. Each base includes a wide, upward facing trough approximating the placement and curvature of teeth within a dental quadrant. The upper surface of each insert is attached to a positive dental mold by means of protrusions that extend from the top horizontal surface of the insert, the protrusions being encased within the mold material. Positive positional relationship is maintained between each base and its mating insert by the use of an interlocking and non-recurring geometric pattern that is carried by the internal vertical walls of the trough in the base, and by a matching geometric pattern that is carried by the outer vertical walls of two vertically downward extending ribs on the underside of the insert. A second deeper, narrower and centrally located trough is formed in each base. This second trough mates with a third center rib that protrudes from the bottom surface of each insert. The insert's center rib contains a retainer bead along both vertical side walls. This bead provides a snap-lock fit into a corresponding negative indentation formed along the vertical side walls of the center trough in each base. The center rib in each insert contains cylindrical cavities which allow the insertion of standard dental dowels or suitable substitutes.
Dental impression handling tools of the type described above in Nooning are undesirable in that the base comprises a slot into which debris can collect. As a result, often the insert will be unable to secure a proper fit within the base structure, thereby precluding proper alignment, which is highly undesirable.